As known from the prior art process of casting concrete products by extruder type extruding involves feeding concrete mass from the concrete mass hopper of a extruder on top of auger feeders, said auger feeders conveying concrete mass under pressure into a delimited cross-section established by a casting bed, sidewalls advancing along with the casting machine, together with a levelling beam defining the top surface of a product being cast, i.e. into a extruder mold. The extruder mold defines a product to be cast in terms of its cross-sectional shape. The concrete mix under pressure, fed into a extruder mold, is compacted for example by a levelling and/or reciprocating motion of the sidewalls and the levelling beam, as well as by a reciprocating motion of the auger feeder in addition to a rotary motion of the auger feeder responsible for feeding the mass. In the process of casting concrete products with hollow cores by extruding, behind the auger feeders is added hollow-core forming members or hollow-core mandrels. As extruding progresses, the extruder advances along a casting bed in response to a reaction force resulting from the feeding of concrete mass by the auger feeders, which advancement of the extruder can be accelerated or decelerated as necessary by means of a drive motor of the extruder apparatus. As the extruder advances, the cast product remains on the casting bed for hardening and curing prior to its possible cutting for defined-length blocks and replacement to storage.
Auger feeders can also be used in extruder types other than extruder types, where the auger feeders can enhance the feeding of concrete mix, for example at a specific feeding stage.
At present, auger feeders are usually attached by way of flanges fixed to a shaft rotating the auger feeder and to the auger feeders. These flanges are fastened to each other by screws extending through unthreaded holes existing in the flanges. An established approach with these attachments is to weld the screw heads securely to the flange in an effort to ensure the durability of the auger feeder attachment in use.
In EP patent publication 2239118 B1 (corresponding FI patent publication 121656 B) is disclosed an auger feeder for concrete mix, comprising a helical segment, which auger feeder comprises an insert mounted on an upstream end of the auger feeder, said insert being manufactured in a material softer than that used for manufacturing the auger feeder's helical segment, and said insert comprising means for fastening the auger feeder to a casting apparatus, which the auger feeder comprises a cast infill cast at least partially over the insert. The downstream end of this know auger feeder has been manufactured as a continuous part of the auger feeder's helical segment of same material, typically of white cast iron, which has good hardness and abrasion resistance but is hard and brittle, thus very difficult to manufacture by chip removing techniques, which has made the manufacturing of the auger feeder slow and costly as a bearing housing is needed at this downstream end of the auger feeder, which is under high abrasive wear and thus very high hardness and abrasion resistance properties are needed.
In FI patent publication 50587 C is disclosed an auger feeder, in which inserts are mounted on a downstream end of the auger feeder.